Apparatus and method for grinding inserts



March 25, 1969 N, F. D, MARTW 3,434,248

APPARATUS AND METHOD FOR GRINDING INSERTS Filed 00t- 20, 1965 Sheet INVENTOR.

APPARATUS AND METHOD FOR GRINDING INSERTS Filed D013. 20, 1965 March 25; 1969 N. F. D. MARTIN Sheet it i INVENTOR. @22 08; xr/amz BY JzW/%fl March 25, 1969 N. F. D. MARTIN 3,434,248

APPARATUS AND METHOD FOR GRINDING INSERTS IN VENTOR.

United States Patent 0 US. Cl. 51-234 28 Claims ABSTRACT OF THE DISCLOSURE A method and apparatus for grinding indexable-throwaway inserts of the type having a pair of parallel faces and a plurality of plane sides thereabout extending be tween the faces with an arcuate surface joining adjacent sides so that one of the faces has a greater area than the other face, and more particularly, to a method and apparatus for rotating a plurality of inserts about an axis which is at an inclined angle relative to the faces for grinding the arcuate surfaces and for grinding the sides so that each of the sides forms an acuate angle with one of the faces and forms an obtuse angle with the other face whereby one face of each insert has a larger area than the other face.

Inserts of the type which may be ground by utilization of the instant invention are frequently utilized in milling head cutters and the like. The inserts are usually made of hard tungstencarbide, titanium, hard steel, or the like. U

Such inserts are frequently secured in a circle about a milling head cutter so that as the milling head cutter rotates the inserts successively engage a workpiece for cutting material from the workpiece. The inserts used in any particular milling head cutter for milling a particular workpiece must be substantially identical in size and shape so that each insert performs an identical cutting function as it contacts the particular workpiece.

The shapes of the inserts used in various milling operations vary widely. But as pointed out above, the inserts normally haveta pair of parallel faces with a plurality of plane sides extending between the faces. Generally, inserts are of one of two broad classes, one class is referred to as a negative rake insert and the other class is referred.

to as a positive rake insert. The plane sides of the negative rake insert are perpendicular to each of the faces of the insert whereas the plane sides in a positive rake insert each form an acute angle wih one of the faces of the insert and form an obtuse angle with the other face of the insert so that one of the faces has a greater area than the other face. That is to say, the plane sides in a positive rake insert are disposed so that they converge, as would the sides in a horizontal layer of a pyramid. In addition, the inserts normally have rounded corners or arcuate surfaces which join adjacent plane sides.

Various indexable-throwaway inserts may have any number of plane sides, i.e., a substantially triangular shaped insert has three plane sides, a substantially rectangular shaped insert has four plane sides, and so on. In addition to the various numbers of sides which a particular insert may have, the radius evolving the arcuate surface joining adjacent sides may vary between different inserts. That is to say, a group of inserts suitable for use in one milling operation may have the same number of plane sides and be substantially the same overall size as a second group of inserts utilized in another milling operation, yet the two groups of inserts may differ only in that one group of inserts has arcuate surfaces which are defined by a smaller radius than the radius defining the arcuate surfaces of the other group of inserts.

Positive rake indexable-throwaway inserts are normally ice made or finished by grinding, and theretofore this grinding process has been very complex due to the various shapes, sizes, and different radii defining the arcuate surfaces of the various surfaces. More specifically, the grinding of positive rake inserts has heretofore required a separate and distinct grinding operation for each of the plane sides and for each arcuate surface. And generally, in the utilization of known apparatus, it has heretofore been possible to grind only one such insert at a time. In essence, the prior methods and apparatuses utilized in grinding positive rake indexable-throwaway inserts all have the common disadvantage of requiring the removal and repositioning of the insert in an apparatus a burdensome number of times depending upon the number of plane sides and associated arcuate surfaces to be ground on a particular insert. Methods and apparatuses heretofore utilized frequently require that one insert be secured in an apparatus relative to an abrasive grinding wheel so that a portion of the insert may be ground, but in order to grind another portion of the insert, i.e., side or arcuate surface, the insert must be removed from the apparatus and repositioned relative to the abrasive grinding wheel and resecured in the apparatus for subsequent grinding for each respective portion. Furthermore, electrostatic grinding cannot be accomplished in heretofore known machines for grinding inserts because the waste resulting from the electrostatic grinding causes the complex mechanisms utilized in such machines to malfunction.

The various methods and apparatuses utilized heretofore for grinding positive rake indexab le-throwaway inserts are therefore complex, expensive, require large amounts of time for grinding particular inserts, are subject to error in grinding, and are not readily adaptable for grinding inserts of various configurations.

Accordingly, it is an object and feature of this invention to provide a work holder which is simple in construction and may be utilized to grind one or more positive rake inserts at one time.

Another object and feature of this invention is to provide a work holder for grinding positive rake indexablethrowaway inserts of the type having a pair of parallel faces and a plurality of plane sides thereabout extending between the faces with an arcuate surface joining and preferably tangent to adjacent sides, which work holder may be adjusted to grind arcuate surfaces defined by various radii as determined by the adjustment.

A further object and feature of this invention is to provide a work holder for grinding positive rake indexablethrowaway inserts of the type having a pair of parallel faces and a plurality of plane sides thereabout extending between the faces with an arcuate surface joining adjacent sides whereby the work holder may be utilized to grind two or more adjacent plane sides and the arcuate surfaces therebetween without removing the insert from the apparatus.

In general, these and other objects and features of this invention are attained by a work holder including a fixture adapted to be mounted on a grinding machine for rotation about a first axis. A first clamping member has a first end disposed in the fixture and extends from the fixture to present a first plane clamping surface. A second clamping member is coaxial with the first clamping member about a second axis which is in spaced parallel relationship with the first axis and is slidably disposed in the fixture and presents a second plane clamping surface. The clamping surfaces of the respective clamping members are normally disposed in respective spaced parallel planes which are at an inclined angle relative to the first and second axes. There is also included an actuating means for sliding the second clamping member toward the first clamping member and for maintaining the second clamping member so that a plurality of inserts may be retained between the clamping surfaces. An adjustment means operatively interconnects the fixture and the machine for selectively changing the distance between the first and second axes to establish the radius of the arcuate surfaces to be ground to extend between adjacent sides of the inserts. Also, a positioning means is removably attached to one of the clamping members for engaging a plurality of inserts which are disposed between the clamping surfaces to position the inserts in a predetermined relationship with the clamping members before the inserts are clamped between the clamping surfaces. Once the inserts are clamped between the clamping surfaces, the work holder is positioned relative to an abrasive grinding wheel, which may be an electrostatic grinding device, for grinding one of the plane sides of the inserts. Once a first plane side of the insert has been ground, the fixture is rotated about the first axis, which is at an inclined angle relative to the faces of the inserts and is in parallel and spaced relationship with the second axis, to grind an arcuate surface on the particular number of inserts held in the fixture. Once the arcuate surface has been ground, a second plane side is ground on the inserts. Stop means interconnects the fixture and the machine for limiting the amount of rotation of the fixture in correlation with the number of degrees each of the arcuate surfaces evolves. Since the sides of a positive rake insert converge toward one another, the inserts must be repositioned after the second side has :been ground. The repositioning of the inserts is accomplished by removing the stack of inserts from between the clamping surfaces and rotating the stack of inserts about an axis passing through the faces thereof and sliding the inserts relative to each other and reclamping the inserts between the clamping surfaces. Of course, the first two sides of the inserts may be ground in one machine and removed and clamped in a second machine for the remaining grinding instead of doing all of the grinding in one machine constructed in accordance with the instant invention.

Other objects and attendant advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIGURE 1 is a side elevational view partly broken away of a preferred embodiment of the present invention;

FIGURE 2 is a view taken substantially along line 22 of FIGURE 1;

FIGURE 3 is a view taken substantially along line 3-3 of FIGURE 1;

FIGURE 4 is an enlarged fragmentary view in cross section taken substantially along line 4-4 of FIGURE 2;

FIGURE 5 is a cross-sectional view taken substantially along line 5-5 of FIGURE 1;

FIGURE 6 is an enlarged fragmentary cross-sectional view taken substantially along line 66 of FIGURE 1;

FIGURE 7 is a cross-sectional view taken substantially along line 77 of FIGURE 1;

FIGURE 8 is an enlarged cross-sectional view taken substantially along line 88 of FIGURE 1;

FIGURE 9 is an enlarged isometric view of an indexable-throwaway insert of the positive rake type which may be ground in accordance with the instant invention;

FIGURE 10 is an enlarged fragmentary view partly in cross section of the preferred embodiment of the present invention and illustrating a positioning means to position inserts in a predetermined relationship therewith;

FIGURE 11 is a cross-sectional view taken substantially along line 1111 of FIGURE 10;

FIGURE 12 is a cross-sectional view taken substantially along line 1212 of FIGURE 10;

FIGURE 13 is a fragmentary cross-sectional view of a modification of the positioning means;

FIGURE 14 is a cnoss-sectional view taken substantially along line 1414 of FIGURE 13; and

FIGURE 15 is a cross-sectional view taken substantially along line 1515 of FIGURE 14.

Referring now to the drawings, wherein like numerals indicate like or corresponding parts throughout the several views, there is generally shown at 10 a work holder for grinding positive rake indexable-throwaway inserts, generally shown at 12.

A positive rake indexable-throwaway insert of the type which may be ground in accordance with the instant invention is generally shown at 14 in FIGURE 9. The insert 14 has a pair of parallel faces, one of which is shown at 16, and a plurality of plane sides 18 are disposed thereabout and extend between the faces 16. Also, arcuate surfaces 20 join adjacent sides 18 and are preferably tangent to the adjacent sides 18. Each of the sides 18 forms an acute angle with one of the faces 16 and forms an obtuse angle with the other of the faces 16 so that one of the faces 16 has a larger area than the other face 16. That is to say, the sides 18 converge. As alluded to previously, indexa'ble-throwaway inserts of the type which may be ground in accordance with the instant invention may have a various number of plane sides 18 and it is to be understood that the insert 14 in FIGURE 9 is merely illustrative and that instead of having a substantially triangular configuration as the insert 14, inserts having a substantially rectangular shape, octagonal shape, hexaonal shape, etc., may be ground in accordance with the instant invention.

Each of the arcuate surfaces 20 joins adjacent plane sides 18 and is defined by an arc struck about or concentric to the axis 24, which is at an angle other than normal to the faces 16. As pointed out hereinbefore, each insert of substantially the same configration and size may have various arcuate surfaces as defined by arcs having different radii; for example, the arcuate surface may be defined by an arc evolved about the axis 22, which are has a larger radius than the arc evolved about the axis 24, as is illustrated in phantom in FIGURE 9.

The indexable-throwaway inserts illustrated generally at 12 are to be ground in accordance with the instant invention to the configuration illustrated by the insert 14 in FIGURE 9. The inserts 12 are held in position by the work holder 10 for grinding contact with the abrasive grinding wheel 26, which abrasive grinding wheel may be an electrostatic grinding device.

The work holder 10 comprises a holding means for rotating at least one insert, preferably a plurality as illustrated, about a first axis 24 which is at an inclined angle relative to the faces 16 of the inserts 12 for grinding the arcuate surfaces 20 and for grinding the sides 18 so that each of the sides 18 forms an acute angle with one of the faces 16 and forms an obtuse angle with the other of the faces 16 so that one of the faces has a larger area than the other. More particularly, the holding means includes a fixture 30, clamping means generally shown at 32, and control means generally shown at 34.

The fixture 30 is adapted to be mounted between first and second mounts 36 and 38, as will be more fully hereinafter described. The mounts 36 and 38 are secured by any appropriate means, such as the bolts 40, to the table or base plate 42 of a grinding machine. A table, such as table 42, is usually provided on grinding machines and is operatively connected to a mechanism for moving the table 42 so that the mounts 36 and 38 are moved in particular paths relative to the grinding wheel 26. The fixture 30 is mounted between the first and second mounts 36 and 38 on the grinding machine for rotation about a first axis 24.

The clamping means 32 is operatively connected to the fixture 30 for holding the inserts 12 at an inclined angle relative to the axis 24' and in a predetermined position relative to the second axis 25 which is in parallel and spaced relationship with the axis 24'. The clamping means 32 includes a first clamping member 44 which has a first end rotatably disposed in the fixture 30 and extends from the fixture 30 to present afirst plane clamping surface 45. The clamping member 44 is journaled in a sleeve or bushing 46 which is in turn disposed in the fixture 30. A ball bearing 47 is disposed at the first end of the clamping member 44 and the clamping member 44 is freely rotatable within the sleeve 46.

The clamping means 32 also includes a second clamping member 52 which is coaxial with the first clamping member 44 about the axis 25, which axis 25 is in spaced parallel relationship with the axis 24. The second clamping member 52 is rotatably and slidably disposed in the fixture 30 and presents a second plane clamping surface 48. The clamping surfaces 45 and 48 are normally disposed in respective spaced parallel planes which are at an angle other than normal relative to the axes 24' and 25, thereby positioning the inserts 12 such that the faces 16 thereof are disposed at an inclined angle relative to the axes 24' and 25.

The clamping means 32 also includes an alignment means, generally shown at 51, for maintaining the clamping members 44 and 52 in fixed positions relative to one another and relative to the second axis 25 when the inserts 12 are clamped therebetween. The alignment means 51 includes a pin 53 which is inserted in a hole 55 in the clamping member 44 and a hole 57 in the other clamping member 52. The alignment means 51 is necessary since, upon clamping of the inserts 12 between the clamping surfaces 45 and 48, the clamping member 44 tends to move upwardly as viewed in FIGURES 2 and and clamping member 52 tends to move downwardly as viewed in FIGURES 2 and 10. Thus, the pin 53 prevents relative movement between the clamping members 44 and 52.

The clamping means 32 also includes an actuating means, generally shown at 54, for sliding the second clamping member 52 toward the first clamping member 44 and for maintaining the second clamping member 52 so that the inserts 12 may be retained between the clamping surfaces 45 and 48. The actuating means 54 is more clearly shown in FIGURE 4 and includes a ball 56 disposed in the fixture 30 in abutting relationship with the end of the clamping member 52. There is also included a plunger 58 disposed for movement in the fixture 30 and in abutting relationship with the ball 56. The actuating means 54 also includes an overcenter locking device for moving the plunger 58 and for maintaining the plunger 58 in a predetermined position to maintain the inserts 12 between the clamping surfaces 45 and 48. The overcenter locking device comprises the block 60 which is pivotally connected to the plunger 58 by the pin 62 and pivotally connected to a slide bar 64 by the pin 66. A handle 68 extends outwardly from the block 60 and is attached thereto by the pin 70. The slider bar 64 has a slanted surface 72 which engages the cone-shaped end of the adjustment screw 74. The clamping means 32 may be released by moving the handle 68 toward the position shown in phantom. A stack of inserts 12 may be placed between the clamping surfaces 45 and 48 and the handle 68 moved to the position shown in solid lines in FIGURE 4 to clamp the inserts between the clamping members 44 and 52. The actuating means 54 is locked in the position shown in solid lines in FIGURE 4 due to the fact that once the handle 68 is rotated to the position illustrated in solid, the center of the pin 62 is slightly below the center of the pin 66 such that forces acting on the block 60 by the slider bar 64 and the plunger 58 create a moment tending to rotate the block 60 in a counterclockwise direction as viewed in FIGURE 4, thereby locking the handle 68 in position to securely retain the inserts 12 between the clamping members 44 and 52. The screw 74 is utilized to adjust the lateral movement of the slider bar 64 such that when a particular number of inserts are disposed between the clamping surfaces 45 and 48 only a minute movement of the handle 68 is required to securely lock the inserts between the clamp- 6 ing members 44 and 52. The plunger 58, block 60, slider bar 64, and handle 68, therefore, provide an overcenter locking device. I

The control means 34 selectively allows the clamping members 44 and 52 to be rotated about the axis 25 relative to the fixture 30. It will be understood, however, upon familiarization of the operation of the instant invention as will become clear hereinafter, that the clamping memhers 44 and 52 need not he rotatable relative to the fixture 30 and hence the control means is not essential to the operation of the instant invention. The control means 34 is most clearly shown in FIGURES 2 and 8 and includes a portion 76 of the clamping member 52, which portion 76 has a slot 78 therein. A selector pin 80 is slidably disposed in the fixture 30 for insertion into the slot 78 to prevent rotation of the clamping member 52 relative to the fixture 30. The selector pin 80, as is more clearly shown in FIGURE 8, has an enlarged portion 82 with a beveled end 84 and a knurled knob 86. The selector pin 80 is slidably disposed in a bushing 88, which is retained in the fixture 30, and a spring abuts the enlarged portion 82 and is held in place by a threaded cap 92, the cap 92 being threaded on the end of the sleeve or bushing 88. The spring 90 coacts with the fixture 30 and the selector pin 80 to bias the selector pin 80 into the slot 78. To prevent movement of the selector pin 80 out of the slot 78 when forces are applied to the inserts by grinding, a locking means comprising the pin 81 is inserted through the cap 92 and the selector pin 80. A spring 83 is attached to the lower end of the pin 81 to retain the pin 81 in position.

The work holder 10 also includes adjustment means, generally shown at 98, which operatively interconnects the fixture 30 with the mounts 36 and 38 for selectively changing the distance between the axes 24' and 25 to establish the radius of the arcuate urfaces 20 which extend between adjacent sides 18 of the inserts 12. The adjustment means 98 includes a first support pin 100, which has a cone-shaped end and extends from the first mount 36, and a second support pin 102, which has a cone-shaped end and extends from the second mount 38. The support pins 100 and 102 are coaxial about the first axis 24. The fixture 30 has a first dovetail slot 104 in the first end thereof and a second dovetail slot 106 in the second end thereof.

A first block 108, having a trapezoidal cross section, is disposed in the first dovetail slot 104. A first retaining means comprising a spacer plate 110' and a setscrew 112 selectively prevents relative movement between the block 82 and the fixture 30. The spacer plate 110 is disposed in the dovetail slot 104 with the block 108 so that the setscrew 112 may 'be tightened against the spacer plate 110 and the block 108 in the dovetail slot 104 to prevent relative movement between the block 108 and the fixture 30. The block 108 has a cone-shaped recess 114 for receiving the cone-shaped end of the support pin 100. The support pin 100 is secured to or integral'with the arcuate member 116 which is clamped in the mount 36 by the bolt 118.

The adjustment means 98 also includes a second block 120 which has a trapezoidal cross section and is disposed in the dovetail slot 106. There is also included a second retaining means comprising the spacer plate 122 and a setscrew 124 for preventing relative movement between the block 120 and the fixture 30. The second spacer plate 122 is disposed in the dovetail slot 106 with the block 120 so that they may be engaged by the setscrew 124 which is threadedly disposed in the fixture 30 to force the spacer plate 122 against the block 120 for preventing relative movement between the block 120 and the fixture 30. The second block 120 has a cone shaped recess 126 therein for receiving the cone-shaped end of the second pin 102. The adjustment means 98, therefore, controls the distance between the axes 24 and 25 which in turn controls the radius of the are of the arcuate surfaces 20 to be ground on the inserts 12.

The work holder 10 also includes a stop means, generally shown at 128, for limiting the amount of rotation of the fixture 30 in correlation with the number of degrees each of the arcuate surfaces evolves. The stop means 128 includes a stop plate 130 removably mounted on the first mount 36 by the studs 132. First and second stop pins 134 extend from the stop plate 130 toward the fixture 30. A third stop pin 136 extends from the block 108 toward the mount 36 for engaging the first and second stop pins 134 respectively to define a predetermined arc of rotary move-ment of the fixture 30 about the axis 24.

The work holder 10 also includes a positioning means, which is most clearly illustrated in FIGURES 10 through 15 and which is removably disposed on one of the clamping members 44 and 52 of the fixture 30 for engaging the inserts 12 to position the inserts 12 in a predetermined relationship with the clamping members 44 and 52 of the fixture 30. The positioning means includes a gage plate 140 and gage blocks 142 and 144. The gage plate 140 is adapted to be disposed in a predetermined position relative to the clamping member 44 and 52 for abutting engagement with one of the sides 18 of the inserts 12 to limit movement of the inserts 12 in a first direction downward, as viewed in FIGURE 10. The second clamping member 52 presents a first surface 146 which is in spaced relationship to the inserts 12 and the axes 24 and 25. The gage plate 140 has a second surface 148 Which matingly engages the surface 146 of the clamping member 52 for positioning the gage plate 140 in the predetermined position relative to the clamping members 44 and 52. There is included a securing means comprising the threaded fastener 150 which threadedly engages the clamping member 52 and the gage plate 140 to maintain the gage plate 140 in position.

As is best illustrated in FIGURE 10, the surface 146 of the clamping member 152 is machined to very accurate tolerance as is the surface 148 on the gage plate 140 so that the gage plate 140 presents a finished surface 152 for abutting the inserts 12 so that the inserts are disposed in a predetermined relationship with the axis 25. As will be apparent, machined gage plates 140 of various thicknesses will be utilized for inserts 12 of different sizes. Furthermore, a gage plate 140 of one thickness will be utilized when abutting an unground side of the inserts 12, as illustrated in FIGURE 10, and a gage block 140 having a greater thickness will abut a ground side 18 of the inserts 12, as illustrated in FIGURE 13. That is to say, when the inserts 12 are initially placed for clamping between the clamping surfaces 45 and 58, none of the sides 18 have been ground thereon and therefore a gage plate 140 having a predetermined thickness will be utilized to position the inserts 12, but once one or more of the sides 18 have been ground the inserts will be repositioned and a ground side 18 is positioned against a different gage plate 140 which will have a greater thickness to compensate for the material ground from the finished side of the inserts 12 to position the inserts 12 in a predetermined position relative to the axis 25 to grind other sides 18.

The positioning means also includes gage blocks 142 and 144, each of which has a first portion thereof adapted to engage one of the clamping members 44 and 52 to dispose the gage block in a specified position relative to the clamping member and a second portion adapted to engage the inserts 12 for limiting linear movement of the inserts 12 in a direction which is perpendicular to the direction in which they are limited in movement by the gage plate 140 and for limiting movement of the inserts 12 in a direction which is opposite to the direction in which the inserts are limited in movement by the gage plate 140. Thus, the inserts may be positioned in the predetermined relationship with the clamping members 44 and 52 for clamping therebetween. As alluded to hereinbefore, there are two modifications of the gage block illustrated; that is, the gage block 142 and the gage block 144, each of which differs from the other essentially only in the precise position of the surfaces presented.

The gage block 142 is utilized initially to position inserts 12 which have not yet been ground. The block 142 has a first portion which is a V-shaped groove 154 for enagaging an arrowhead-shaped portion 156 of the clamping member 52 so that there is contiguous mating engagement between the V-shaped groove 154 and the arrowhead-shaped portion 156. The groove 154 and the portion 156 are machined to precise tolerances so that the block 142 presents a pair of surfaces 158 for engaging the inserts 12 so that the inserts are disposed between the surfaces 158. As is illustrated in FIGURES 10, 11 and 12, the gage block 142 rests in a specified position relative to the clamping members 44 and 52 due to the contiguous engagement between the V-shaped groove 154 and the arrowhead-shaped portion 156 such that the surfaces 158 are in a specified position to engage the inserts 12. Thus, the inserts 12 are precisely positioned between the surfaces 158 of the gage block 142 and the surface 152 of the gage plate 140 so that the clamping members 44 and 52 may be moved together to precisely secure the inserts 12 between the clamping surfaces and 48. Once the inserts are held between the clamping surfaces 45 and 48, the gage block 142 is removed. Once the gage block 142 has been removed, the mounts 36 and 38 may be positioned so that the grinding wheel 26 engages the inserts 12 to grind one of the plane sides 18 into the inserts 12. When the first side 18 is ground into the inserts 12, the fixture 30 is disposed at an extreme limit of rotary movement as defined by the engagement of the stop 136 with one of the stops 134. Once a first side 18 has been ground into the inserts 12, the fixture 30 is rotated about the axis 24, as defined by the mount pins and 102, to grind a first arcuate surface 20 into the inserts 12, as is illustrated in FIGURE 2. The fixture 30 is rotated to grind the first arcuate surface 20 until further rotary movement is limited by the engagement of the stop 134 with the other of the stops 136. Thus, the rotary movement of the fixture 30 is limited at a position where the grinding wheel 26 is disposed for grinding a second plane side 18 of the inserts 12.

As was pointed out hereinabove, the adjustment of the distances between the axes 24' and 25 by the adjustment means 98 determines the length of the radius defining the arcuate surfaces 20 joining adjacent sides 18 of the inserts 12 being ground.

Once two sides 18 and the joining arcuate surface 20 of the inserts 12 have been ground, the inserts 12 are removed from the clamping members 44 and 52 and are rotated about an axis which passes through the faces 16 of the inserts 12 and are allowed to slide relative to one another. The inserts 12 are then placed between the clamping surfaces 45 and 48 with a ground side thereof resting upon the surface 152 of a gage plate 140. This reorientation of the inserts 12 after the first two sides 18 have been ground therein is necessary in order to grind subsequent sides 18 so that all of the sides 18 converge. Of course, this reorientation may be necessarily performed more than once depending upon the total number of sides 18 to be ground in a particular insert.

When the inserts 12 have been repositioned, one of the ground sides 18 engages the gage plate however, as was alluded to hereinbefore, when the inserts 12 are removed from the clamping members 44 and 52 for repositioning, a new gage plate 140 is secured to the clamping member 52. A new gage plate 140 is necessarily utilized since the new gage plate 140 will engage a finished or ground side 18 of the inserts 12 and therefore must be of a slightly greater thickness to compensate for the material removed to grind the sides 18 so that the inserts will be positioned properly for clamping between the clamping surfaces 45 and 48.

Once the inserts have been reoriented, the gage block 144 is positioned upon the arrowhead-shaped portion 156 of the clamping member 52 and presents a machined surface 160 for engaging the other ground side 18 of the inserts 12. Thus, the surface 160 compensates for the reremoval of material from the inserts 12 by the grinding of the other side .18 thereof. The block 144 includes means comprising the plunger 162 attached to the bar 164 for engaging the inserts 12 to affirmatively position the inserts 12 against the machined surface 160. The side of the inserts which the bar 164 contacts is an unground side, thus a ground side 18 of the inserts 12 is affirmatively positioned against the machined surface160 of the gage block 144 so that the inserts 12 are precisely positioned due to the engagement of a machined side thereof with :tne gage plate 140 and the engagement between a ground side 18 and the machined surface 160 of the gage block 144. As an alternative the portion of the gage block 144 supporting the plunger 162 may be eliminated to provide an opening for the operator to push the inserts 12 against the surface 160 with a finger.

It will be understood, of course, that although the present invention has been described in connection with the grinding of a substantially triangular-shaped insert, such as insert 14 shown in FIGURE 9, the invention is equally suitable for grinding inserts of the positive rake type which have any number of sides so as to be rectangular, octagonal, hexagonal, etc.

It is further to be understood that the apparatus illustrated in the drawings is merely a preferred embodiment of an apparatus suitable for carrying out a method of grinding indexable-throwaway inserts of the type having a pair of parallel faces and a plurality of plane sides thereabout extending between the faces with an arcuate surface joining adjacent sides and that other apparatuses may be utilized to perform the method of grinding such inserts, since other apparatuses may be utilized to grind inserts of the positive rake type so long as the inserts are positioned in a fixed position between a pair of movable parallel clamping surfaces, which surfaces are at an inclined angle relative to the direction of movement thereof, and thereafter clamping the inserts between the clamping surfaces so that the inserts are disposed in a fixed position relative to an axis which is at an inclined angle relative to the faces of the inserts. A first side of the inserts is then ground and the inserts are thereafter rotated about the axis which is at an inclined angle relative to the faces of the inserts to grind a first arcuate surface and to grind a second side of the inserts. Once two sides and the joining arcuate surface of the inserts has been ground, the inserts are repositioned between the clamping surfaces to grind subsequent sides so that all of the sides of the insert converge whereby one face of each insert has a larger area than the other face thereof to form a positive rake insert.

It is also to be understood that the instant invention may be utilized to grind inserts which have no discernible arcuate surfaces so that the respective sides meet at points or apexes.

The invention has been described in an illustrative manner and it is to be understod that the terminology which has been used is intended to be in the nature of words of description rather than of limitation.

Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A work holder for use in grinding indexable-throwaway inserts of the type having a pair of parallel faces and a plurality of plane sides thereabout extending between said faces with an arcuate surface joining adjacent sides, said work holder comprising; holding means for rotating at least one of said inserts about a first axis which is at an inclined angle relative to said faces for grinding said arcuate surfaces and for grinding said sides so that each of said sides forms an acute angle with one of said faces and forms an obtuse angle with the other of said faces so that one of said faces has a larger area than the other of said faces, said holding means including, a fixture adapted to be mounted on a machine for rotation about said first axis, clamping means operatively connected to said fixture and applying clamping forces along a second axis which is in parallel and spaced relationship with said first axis for holding said inserts at said inclined angle, and adjustment means operatively interconnecting said fixture and said machine for selectively changing the distance between said first and second axes to establish the radius of said arcuate surfaces which extend between adjacent sides of said inserts.

2. A work holder as in claim 1 including stop means for limiting the amount of rotation of said fixture in correlation with the number of degrees each of said arcuate surfaces evolves.

3. A work holder for use in grinding indexable-throwaway inserts of the type having a pair of parallel faces and a plurality of plane sides thereabout extending between said faces with an arcuate surface joining adjacent sides, said work holder comprising; holding means for rotating at least one of said inserts about a first axis which is at an inclined angle relative to said faces for grinding said arcuate surfaces and for grinding said sides so that each of said sides forms an acute angle with one of said faces and forms an obtuse angle with the other of said faces so that one of said faces has a larger area than the other of said faces, said holding means including, a fixture adapted to be mounted on a machine for rotation about said first axis, clamping means operatively connected to said fixture and applying clamping forces along a second axis which is in parallel and spaced relationship with said first axis for holding said inserts at said inclined angle, and stop means for limiting the amount of rotation of said fixture in correlation with the number of degrees each of said arcuate surfaces evolves.

4. A work holder for use in grinding indexable-throwaway inserts of the type having a pair of parallel faces and a plurality of plane sides thereabout extending between said faces with an arcuate surface joining adjacent sides, said work holder comprising; a fixture for holding said inserts, and positioning means removably disposed on said fixture for engaging said inserts to position said inserts in a predetermined relationship with said fixture, said positioning means including, a gage plate adapted to be disposed in a predetermined position relative to said fixture for abutting engagement with one of said sides of said inserts to limit movement of said inserts in a first direction, said fixture presenting a first surface and said gage plate having a second surface matingly engaging said first surface for positioning said gage plate in said predetermined position, and securing means engaging said fixture and said gage plate to maintain said gage plate in said predetermined position, and an independent gage block having a first portion thereof adapted to engage said fixture to dispose said gage block in a specified position relative to said fixture and a second portion adapted to engage inserts for limiting linear movement of the inserts in a direction which is perpendicular to said first direction and for limiting movement of the inserts in a direction opposite to said first direction.

5. A work holder as set forth in claim 4 wherein said second portion of said gage block includes at least one machined surface for engaging a ground side of said inserts, and including means operatively connected to said gage block for engaging said inserts to afiirmatively position said inserts against said machined surface.

6. A work holder as set forth in claim 4 wherein said second portion of said gage block includes surfaces so that part of each of said inserts is disposed therebetween when said first portion thereof matingly engages said fixture.

7. A work holder as set forth in claim 6 wherein said first portion of said gage block is a V-shaped groove and said fixture includes an arrowhead-shaped portion for contiguous mating engagement with said V-shaped groove.

8. A work holder for use in grinding indexable-throwaway inserts of the type having a pair of parallel faces and a plurality of plane sides thereabout extending between said faces with an arcuate surface joining adjacent sides, said work holder comprising; holding means for rotating at least one of said inserts about a first axis which is at an inclined angle relative to said faces for grinding said arcuate surfaces and for grinding said sides so that each of said sides forms an acute angle with one of said faces and forms an obtuse angle with the other of said faces so that one of said faces has a larger area than the other of said faces, said holding means including, a fixture adapted to be mounted on a machine for rotation about said first axis, clamping means operatively connected to said fixture for holding said inserts at said angle, said clamping means including, a first clamping member having a first end disposed in said fixture and extending from said fixture to present a first plane clamping surface, a second clamping member coaxial with said first clamping member about a second axis which is in spaced parallel relationship with said first axis and slidably disposed in said fixture and presenting a second plane clamping surface, said clamping surfaces disposed in respective spaced parallel planes which are at said angle to said axes, actuating means for sliding said second clamping member toward said first clamping member and for maintaining said second clamping member so that inserts may be retained between said clamping surfaces, and positioning means removably disposed on said second clamping member for engaging said inserts to position said inserts in a predetermined relationship with said clamping members, said positioning means including, a gage plate adapted to be disposed in a predetermined position relative to said clamping members for abutting engagement with one of said sides of said inserts to limit movement of said inserts in a first direction, said second clamping member presenting a first surface in spaced relationship to said second axis, said gage plate having a second surface matingly engaging said first surface for positioning said gage plate in said predetermined position, securing means engaging said second clamping member and said gage plate to maintain said gage plate in said predetermined position, and a gage block having a first portion thereof adapted to engage said second clamping member to dispose said gage block in a specified position relative to said clamping members and a second portion adapted to engage inserts disposed between said clamping members for limiting linear movement of said inserts in a direction which is perpendicular to said first direction and perpendicular to said axes and for limiting movement of said inserts in a direction opposite to said first direction so that said inserts may be positioned in said predetermined relationship for clamping thereof between said clamping surfaces.

9. A work holder as set forth in claim 8 wherein said second portion of said gage block includes at least one machined surface for engaging a ground side of said inserts, and including means operatively connected to said gage block for engaging said inserts to afiirmatively position said inserts against said machined surface.

10. A work holder as set forth in claim 9 wherein said second portion of said gage block includes surfaces so that part of each of said inserts is disposed therebetwe en when said first portion thereof matingly engages said fixture.

11. A work holder as set forth in claim 10 wherein said first portion of said gage block is a V-shaped groove and said second clamping member includes an arrowheadshaped portion for contiguous mating engagement with said V-shaped groove.

12. A work holder for use in grinding indexable-throwaway inserts of the type having a pair of parallel faces and a plurality of plane sides thereabout extending between said faces with an arcuate surface joining adjacent sides, said work holder comprising; holding means for rotating at least one of said inserts about a first axis which is at an inclined angle relative to said faces for grinding said arcuate surfaces and for grinding said sides so that each of said sides forms an acute angle with one of said faces and forms an obtuse angle with the other of said faces so that one of said faces has a larger area than the other of said faces, said holding means including, a fixture adapted to be mounted between first and second mounts for rotation about said first axis, clamping means operatively connected to said fixture for holding said inserts at said angle, said clamping means including, a first clamping member having a first end rotatably disposed in said fixture and extending from said fixture to present a first plane clamping surface, a second clamping member coaxial with said first clamping member about a second axis which is in spaced parallel relationship with said first axis and rotatably and slidably disposed in said fixture and presenting a second plane clamping surface, said clamping surfaces normally disposed in respective spaced parallel planes which are at said angle relative to said axes, actuating means for sliding said second clamping member toward said first clamping member and for maintaining said second clamping member so that said inserts may be retained between said clamping surfaces, control means for selectively allowing said clamping members to be rotated about said second axis relative to said fixture, and adjustment means operatively interconnecting said fixture and said first and second mounts for selectively changing the distance between said first and second axes to establish the radius of said arcuate surfaces which extend between adjacent sides of said inserts.

13. A work holder for use in grinding indexable-throwaway inserts of the type having a pair of parallel faces and a plurality of plane sides thereabout extending between said faces with an arcuate surface joining adjacent sides, said work holder comprising; holding means for rotating at least one of said inserts about a first axis which is at an inclined angle relative to said faces for grinding said arcuate surfaces and for grinding said sides so that each of said sides forms an acute angle with one of said faces and forms an obtuse angle 'with the other of said faces so that one of said faces has a larger area than the other of said faces, said holding means including, a fixture adapted to be mounted between first and second mounts on a machine for rotation about said first axis, clamping means operatively connected to said fixture for holding said inserts at said angle, said clamping means including, a first clamping member having a first end rotatably disposed in said fixture and extending from said fixture to present a first plane clamping surface, a second clamping member coaxial with said first clamping member about a second axis which is in spaced parallel relationship with said first axis and rotatably and slidably disposed in said fixture and presenting a second plane clamping surface, said clamping surfaces normally disposed in respective spaced parallel planes which are at said angle relative to said axes, actuating means for sliding said second clamping member toward said first clamping member and for maintaining said second clamping member so that said inserts may be retained between said clamping surfaces, control means for selectively allowing said clamping members to be rotated about said second axis relative to said fixture, adjustment means operatively rotatably interconnecting said fixture and said first and second mounts for selectively changing the distance between said first and second axes to establish the radius of said arcuate surfaces which extend between adjacent sides of said inserts,

and stop means for limiting the amount of rotation of said fixture in correlation with the number of degrees each of said arcuate surfaces evolves.

1-4. A work holder for use in grinding indexable-throwaway inserts of the type having a pair of parallel faces and a plurality of plane sides thereabout extending between said faces with an arcuate surface joining adjacent sides, said work holder comprising; holding means for rotating at least one of said inserts about a first axis which is at an inclined angle relativeto said faces for grinding said arcuate surfaces and for grinding said sides so that each of said sides forms an acute angle with one of said faces and forms an obtuse angle with the other of said faces so that one of said faces has a larger area than the other of said faces, said holding means including, a fixture adapted to be mounted between first and second mounts on a machine for rotation about said first axis, clamping means operatively connected to said fixture for holding said inserts at said angle, said clamping means including, a first clamping member having a first end rotatably disposed in said fixture and extending from said fixture to present a first plane clamping surface, a second clamping member coaxial with said first clamping member about a second axis which is in spaced parallel relationship with said first axis and rotatably and slidably disposed in said fixture and presenting a second plane clamping surface, said clamping surfaces normally disposed in respective spaced parallel planes which are at said angle relative to said axes, actuating means for sliding said second clamping member toward said first clamping member and for maintaining said second clamping member so that said inserts may be retained between said clamping surfaces, control means for selectively allowing said clamping members to be rotated about said second axis relative to said fixture, adjustment means operatively and rotatably in terconnecting said fixture and said first and second mountsfor selectively changing the distance between said first and second axes to establish the radius of said arcuate surfaces which extend between adjacent sides of said inserts, said adjustment means including, a first support pin having a cone-shaped end and extending from said first mount, a second support pin having a cone-shaped end and extending from said second mount, said first and second support pins being coaxial about said first axis, said fixture having a first dovetail slot in the first end thereof and a second dovetail slot in the second end thereof, a first block having a trapezoidal .cross section disposed in said first dovetail slot, first retaining means for selectively preventing relative movement between said first block and said fixture and including, a first spacer plate disposed in said first dovetail slot with said first block, a first setscrew threadedly disposed in said fixture for engaging said first spacer plate, said first block having a cone-shaped recess for receiving said cone-shaped end of said first support pin, a second block having a trapezoidal cross section disposed in said second dovetail slot, second retaining means for selectively preventing relative movement between said second block and said fixture and including, a second spacer plate disposed in said second dovetail slot with said second block, a second setscrew threadedly disposed in said fixture for engaging said second spacer plate, said second block having a coneshaped recess therein for receiving said cone-shaped end of said second support pin, and stop means for limiting the amount of rotation of said fixture in correlation with the number of degrees each of said arcuate surfaces evolves.

15. A work holder for use in grinding indexable-throwaway inserts the type having a pair of parallel faces and a plurality of plane sides thereabout extending between said faces with an arcuate surface joining adjacent sides, said work holder comprising; holding means for rotating at least one of said inserts about a first axis which is at an inclined angle relative to said faces for grinding said arcuate surfaces and for grinding said sides so that each of said sides forms an acute angle with one of said faces and forms an obtuse angle with the other of said faces so that one of said faces has a larger area than the other of said faces, said holding means including, a fixture adapted to be mounted between first and second mounts on a machine for rotation about said first axis, clamping means operatively connected to said fixture for holding said inserts at said angle, said clamping means including, a first clamping member having a first end rotatably disposed in said fixture and extending from said fixture to present a first plane clamping surface, a second clamping member coaxial with said first clamping memher about a second axis which is in spaced parallel relationship with said first axis and rotatably and slidably disposed in said fixture and presenting a second plane clamping surface, said clamping surfaces normally disposed in respective spaced parallel planes which are at said angle relative to said axes, actuating means for sliding said second clamping member toward said first clamping member and for maintaining said second clamping member so that said inserts may be retained between said clamping surfaces, control means for selectively allowing said clamping members to be rotated about said second axis relative to said fixture, adjustment means operatively and rotatably interconnecting said fixture and said first and second mounts for selectively changing the distance between said first and second axes to establish the radius of said arcuate surfaces which extend between adjacent sides of said inserts, said adjustment including, a first support pin having a cone-shaped end and extending from said first mount, a second support pin having a coneshaped end and extending from said second mount, said first and second support pins being coaxial about said first axis, said fixture having a first dovetail slot in the first end thereof and a second dovetail slot in the second end thereof, a first block having a trapezoidal cross section disposed in said first dovetail slot, first retaining means for selectively preventing relative movement be tween said first block and said fixture and including, a first spacer plate disposed in said first dovetail slot with said first block, a first setscrew threadedly diposedin said fixture for engaging said first spacer plate, said first block having a cone-shaped recess for receiving said coneshaped end of said first support pin, a second block having a trapezoidal cross section disposed in said second dovetail slot, second retaining means for selectively .preventing relative movement between said second block and said fixture and including, a second spacer plate disposed in said second dovetail slot with said second block, a second setscrew threadedly disposed in said fixture for engaging said second spacer plate, said second block having a cone-shaped recess therein for receiving said cone-shaped end of said second suport pin, and stop means for limiting the amount of rotation of said fixture in correlation with the number of degrees each of said arcuate surfaces evolves and including, a stop plate removably mounted on said first mount, first and second stop pins extending from said stop plate toward said first end of said fixture, and a third stop pin extending from said first block toward said first mount for engaging said first and second stop pins respectively to define a predetermined arc of rotary movement of said fixture about said first axis.

16. A work holder for use in grinding indexablethrowaway inserts of the type having a pair of parallel faces and a plurality of plane sides thereabout extending between said faces with an arcuate surface joining adjacent sides, said work holder comprising; holding means for rotating at least one of said inserts about a first axis which is at an inclined angle relative to said faces for grinding said arcuate surfaces and for grinding said sides so that each of said sides forms an acute angle with one of said faces and forms an obtuse angle with the other of said faces so that one of said faces has a larger area than the other of said faces, said holding means includ ing, a fixture adapted to be mounted between first and second mounts on a grinding machine for rotation about said first axis, clamping means operatively connected to said fixture for holding said inserts at said angle said clamping means including, a first clamping member hav ing a first end rotatably disposed in said fixture and extending from said fixture to present a first plane clamping surface, a second clamping member coaxial with said first clamping member about a second axis which is in spaced parallel relationship with said first axis and rotatably and slidably disposed in said fixture and presenting a second plane clamping surface, said clamping surfaces normally disposed in respective spaced parallel planes which are at said angle relative to said axes, actuating means for sliding said second clamping member toward said first clamping member and for maintaining said second clamping member so that said inserts may be retained between said clamping surfaces, control means for selectively allowing said clamping members to be rotated about said second axis relative to said fixture, adjustment means operatively and rotatably interconnecting said fixture and said first and second mounts for selectively changing the distance between said first and second axes to establish the radius of said arcuate surfaces which extend between adjacent sides of said inserts, said adjustment including, a first support pin having a cone-shaped end and extending from said first mount, a second support pin having a cone-shaped end and extending from said second mount, said first and second support pins being coaxial about said first axis, said fixture having a first dovetail slot in the first end thereof and a second dovetail slot in the second end thereof, a first block having a trapezoidal cross section disposed in said first dovetail slot, first retaining means for selectively preventing relative movement between said first block and said fixture and including, a first spacer plate disposed in said first dovetail slot with said first block, a first setscrew threadedly disposed in said fixture for engaging said first spacer plate, said first block having a cone-shaped recess for receiving said cone-shaped end of said first support pin, a second block having a trapezoidal cross section disposed in said second dovetail slot, second retaining means for selectively preventing relative movement between said second block and said fixture and including, a second spacer plate disposed in said second dovetail slot with said second block, a second setscrew threadedly disposed in said fixture for engaging said second spacer plate, said second block having a cone-shaped recess therein for receiving said cone-shaped end of said second support pin, and stop means for limiting the amount of rotation of said fixture in correlation with the number of degrees each of said arcuate surfaces evolves and including, a stop plate removably mounted on said first mount, first and second stop pins extending from said stop plate toward said first end of said fixture, a third stop pin extending from said first block toward said first mount for engaging said first and second stop pins respectively to define a predetermined are of rotary movement of said fixture about said first axis, and positioning means removably disposed on said second clamping member for engaging said inserts to position said inserts in a predetermined relationship with said clamping members.

17. A work holder for use in grinding indexablethrowaway inserts of the type having a pair of parallel faces and a plurality of plane sides thereabout extending between said faces with an arcuate surface joining adjacent sides, said work holder comprising; holding means for rotating at least one of said inserts about a first axis which is at an inclined angle relative to said faces for grinding said arcuate surfaces and for grinding said sides so that each of said sides forms an acute angle with one of said faces and forms an obtuse angle with the other of said faces so that one of said faces has a larger area than the other of said faces, said holding means including, a fixture adapted to be mounted between first and sec- 16 ond mounts on a grinding machine for rotation about said first axis, clamping means operatively connected to said fixture for holding said inserts at said angle, said clamping means including, a first clamping member having a first end rotatably disposed in said fixture and extending from said fixture to present a first plane clamping surface, a second clamping member coaxial with said first clamping member about a second axis which is in spaced parallel relationship with said first axis and rotatably and slidably disposed in said fixture and presenting a second plane clamping surface, said clamping surfaces normally disposed in respective spaced parallel planes which are at said angle relative to said axes, actuating means for sliding said second clamping member toward said first clamping member and for maintaining said second clamping member so that said inserts may be retained between said clamping surfaces, control means for selectively allowing said clamping members to be rotated about said second axis relative to said fixture, adjustment means operatively and rotatably interconnecting said fixture and said first and second mounts for selectively changing the distance between said first and second axes to establish the radius of said arcuate surfaces which extend between adjacent sides of said inserts, said adjustment including, a first support pin having a cone-shaped end and extending from said first mount, a second support pin having a cone-shaped end and extending from said second mount, said first and second support pins being coaxial about said first axis, said fixture having a first dovetail slot in the first end thereof and a second dovetail slot in the second end thereof, a first block having a trapezoidal cross section disposed in said first dovetail slot, first retaining means for selectively preventing relative movement between said first block and said fixture and including, a first spacer plate disposed in said first dovetail slot with said first block, a first setscrew threadedly disposed in said fixture for engaging said first spacer plate, said first block having a cone-shaped recess for receiving said coneshaped end of said first suport pin, a second block having a trapezoidal cross section disposed in said second dovetail slot, second retaining means for selectively preventing relative movement between said second block and said fixture and including, a second spacer plate disposed in said second dovetail slot with said second block, a second setscrew threadedly disposed in said fixture for engaging said second spacer plate, said second block having a cone-shaped recess therein for receiving said cone-shaped end of said second support pin, and stop means for limiting the amount of rotation of said fixture in correlation with the number of degrees each of said arcuate surfaces evolves and including, a stop plate removably mounted on said first mount, first and second stop pins extending from said stop plate toward said first end of said fixture, a third stop pin extending from said first block toward said first mount for engaging said first and second stop pins respectively to define a predetermined arc of rotary movement of said fixture about said first axis, positioning means removably disposed on said second clamping member for engaging said inserts to position said inserts in a predetermined relationship with said clamping members, said positioning means including, a gage plate adapted to be disposed in a predetermined position relative to said clamping members for abutting engagement with one of said sides of said inserts to limit movement of said inserts in a first direction, said second clamping member having a first surface in spaced relationship to said second axis and said gage plate having a second surface matingly engaging said first surface for positioning said gage plate in said predetermined position, a securing means engaging said second clamping member and said gage plate to maintain said gage plate in said predetermined position, and a gage block having a first portion thereof adapted to engage said second clamping member to dispose said gage 17 block in a specified position relative to said second clamping member and a second portion adapted to engage inserts disposed between said clamping members for limiting linear movement of said inserts in a direction which is perpendicular to said first direction and perpendicular to said axes and for limiting movement of said inserts in a direction opposite to said first direction.

18. A work holder as set forth in claim 17 including alignment means for maintaining said clamping members in fixed positions relative to one another and relative to said second axis when inserts are clamped between said clamping surfaces.

19. A work holder as set forth in claim 18 wherein said second portion of said gage block includes at least one machined surface for engaging a ground side of said inserts, and including means operatively connected to said gage block for engaging said inserts to affirmatively position said inserts against said machined surface.

20. A work holder as set forth in claim 18 wherein said second portion of said gage block includes surfaces so that part of each of said inserts is disposed therebetween when said first portion thereof matingly engages said fixture.

21. A work holder as set forth in claim 18 wherein said first portion of said gage block is a V-shaped groove and said second clamping member includes an arrowhead-shaped portion for contiguous mating engagement with said V-shaped groove.

22. Positioning means of the type utilized with first and second clamping members to position indexablethrowaway inserts for clamping between said clamping members so that the inserts may be ground on a grinding machine, said positioning means including; a gage plate adapted to be disposed in a predetermined position relative to said clamping members for abutting engagement with said inserts to limit movement of said inserts in a first direction, said gage plate having a first surface for mating engagement with a surface on one of said clamping members and a second surface for engaging said inserts, securing means for maintaining said gage plate in said predetermined position, and an independent gage block having a first portion thereof adapted to engage one of said clamping members to dispose said gage block in a specified position relative to said clamping members and a second portion adapted to engage inserts disposed between said clamping members for limiting movement of said inserts in a direction which is perpendicular to said first direction and for limiting movement of said inserts in a direction opposite to said first direction.

23. Positioning means as set forth in claim 22 wherein said second portion of said gage block includes at least one machined surface for engaging a ground side of said inserts, and means operatively connected to said gage block for engaging said inserts to aflirmatively position the ground side of said inserts against said machined surface.

24. Positioning means as set forth in claim 22 wherein said second portion of said gage block includes surfaces disposed so that part of each insert, disposed between said clamping members, is disposed therebetween when said first portion of said gage block engages one of said clamping members.

25. Positioning means as set forth in claim 24 wherein said first portion of said gage block is a V-shaped groove for contiguous mating engagement with an arrowheadshaped portion on one of said clamping members.

26. A method for grinding indexablethrowaway inserts of the type having a pair of parallel faces and a plurality of plane sides thereabout extending between said faces with an arcuate surface joining adjacent sides, comprising the steps; positioning a plurality of inserts in a fixed position relative to an axis which is at an inclined angle relative to said faces to grind a first side thereof, rotating said inserts about said axis to grind one of said arcuate surfaces in each insert and to grind a second side in each insert, and repositioning said inserts by sliding said inserts relative to one another for positioning said inserts relative to said axis to grind at least one other side and to grind at least one other arcuate surface by rotating said insert about said first axis.

27. A method of grinding indexable-throwaway inserts of the type having a pair of parallel faces and a plurality of plane sides thereabout extending between said faces with an arcuate surface joining adjacent sides, comprising the steps; positioning a plurality of inserts in a fixed position between a pair of movable parallel clamping surfaces which surfaces are at an inclined angle relative to the direction of movement thereof, clamping said inserts between said clamping surfaces so that said inserts are disposed in a fixed position relative to an axis which is at said inclined angle relative to said faces, grinding a first side of said inserts, rotating said inserts about said axis to grind a first arcuate surface and to grind a second side on each of said inserts, removing said inserts from said clamping surfaces to reorient said inserts and sliding said inserts relative to one another, reclamping said inserts between said clamping surfaces with said second side in the grinding position, and rotating said inserts about said axis to grind a second arcuate surface and a third side.

28. The method as set forth in claim 27 including the steps of removing said inserts from between said clamping surfaces and replacing said inserts between said clamping surfaces so that said third side is in the grinding position, and rotating said inserts about said axis to grind a third arcuate surface.

References Cited UNITED STATES PATENTS 1,363,194 12/1920 Koning 51-124 X 1,455,863 5/1923 Bugbee 51-101 2,283,289 5/1942 Roesch 51-124 2,332,421 10/1943 Wildhaber 51-288 2,367,494 1/1945 Gebel 51-220 2,371,515 3/1945 Gorman.

2,454,472 11/1948 Monkley 51-124 X 2,771,723 11/ 1956 Burleson 51-234 X 2,786,312 3/1957 Armitage 51-101 2,932,133 4/1960 Armitage 51-277 X HAROLD D. WHITEHEAD, Primary Examiner.

US. Cl. X.R. 

